1. Field of the Invention
The present invention relates to person-detecting sensors employed in automatic water faucets, automatic flushers for urinals, and in like applications, and to automatic water faucets provided with such sensors.
2. Description of the Related Art
Automatic water faucets that automatically discharge water upon detecting a user's hand waving action have been known to date. A person-detecting sensor for detecting a person having drawn near is incorporated into the automatic water faucets. A person-detecting sensor in which an imaging element such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), and a light-emitting element such as an LED are arranged offset has been proposed as a person-detecting sensor of this sort.
This person-detecting sensor, identifying the position where reflected light, returned from a detection object in response to emitted light, is incident, measures distance to the detection object by the principle known as triangulation, and determines whether the detection object is present within a predetermined detection distance. Person-detecting sensors employing imaging elements enable reflected-light incident position to be identified with high accuracy from the distribution of received-light quantity of each pixel of the imaging element, making highly accurate ranging possible (reference is made to, for example, Patent Document 1).
Patent Document 1 Japanese Pat. App. Pub. No. 2012-77472
At an automatic water faucet on a sink, for example, accumulating water in the palms of the hands would be an assumed usage situation. In such usage situations, in the transition to water accumulating after water discharge has started, air bubbles or the like produced within the accumulated water repeatedly refract and reflect the light, which can end up diffusing the light such as to lower the received-light quantity of reflected light. In this case, the detection may lapse into an unstable state due to a decrease in the received-light quantity of reflected light, risking that the water may be switched off despite the fact of being in use.